1. Field of the Invention
The present invention relates in general to a ring oscillator for a semiconductor device which generates a high voltage for substrate bias and self-refresh operations, and more particularly to a ring oscillator for minimizing power consumption in a ring oscillation circuit thereof.
2. Description of the Prior Art
Referring to FIG. 1, there is shown a circuit diagram of a conventional ring oscillator for a semiconductor device. As shown in this drawing, the conventional ring oscillator comprises a ring oscillation circuit 100 and a driver 101. The ring oscillation circuit 100 includes a NAND gate G1 for NANDing a control signal Cont and a signal at a node N2 and outputting the NANDed result to a node N1, and inverters G2-G5 connected in series between the nodes N1 and N2. The driver 101 includes inverters G6 and G7 connected in series between the node N2 and a node N3.
Only in the case where the control signal Cont is high in logic, the ring oscillation circuit 100 outputs a pulse signal with a predetermined period to the node N2 to supply it to the driver 101.
However, consumption power in the inverters G2-G5 of the ring oscillation circuit 100 is proportioned to the square of an operating voltage in the operating mode where the control signal Cont is high in logic. For this reason, the above-mentioned conventional ring oscillator for the semiconductor device has a disadvantage in that it is large in power consumption.